Shorting strap



April 26, 1960 G. E. GARD SHORTING STRAP Filed Sept. 10. 1957 INVENTOR GEORGE E- CARD ATTORNEY SHORTING STRAP Application September 10, 1957, Serial No. 683,119

4 Claims. (Cl. 339-222) This invention relates to a shorting strap and more particularly to a shorting strap for use in high frequency applications, such as in industrial driers, heaters, and similar installations.

It is well-known that high frequency current in the radio frequency range flows along the outer skin surface of the conductor onto which the high frequency current is impressed. Thus, in applications where a shorting strap is needed, as in tuned inductors, and where the current densities witnessed are high, clamps have been provided on the shorting straps which presented large clamping surface areas for contact with the inductor. The clamping surfaces have been carefully machined to present the optimum surface area of contact between the conductor and the clamp. However, overheating due to high electrical resistance at the clamping surfaces of conductor and shorting strap and even arcing between such surfaces have been encountered in service.

An object of the invention is to provide a shorting strap for high frequency, high energy level applications which will provide a low-resistance connection between conductor and shorting strap.

Another object of the invention is to provide a shorting strap with a low surface area, high pressure connection between conductor and shorting strap.

A further object of the invention is to provide a shorting strap having high current-carrying capacity with a low surface area-high pressure connection between it and the vconductor to which it is attached.

An additional object of the invention is to provide a shorting strap which will automatically accommodate such :minor misalignment as may be encountered in parallel conductors, such as a pair of parallelly disposed legs of :an inductor.

Other objects of the invention will be clear from consideration of the attached drawing, in which:

Figure 1 is a front elevational view of a shorting strap embodying the invention shown in mounted position on 'a pair of the parallel legs of an inductor, portions only of which are shown;

Figure 2 is a top plan view of the system shown in Figure 1;

Figure 3 is a sectional view taken along the line III-III of Figure 2; and

Figure 4 is a side elevational view of the system shown in Figure 1.

nector is constricted. This constricting action is efiected by a pair of hollow head set screws 10 and 11, shown in Figure 1, which pass through drilled and counterbored openings provided in one arm 12 of the connector and are received within aligned threaded openings in the other arm 13 of the connector, as shown in Figures 2 and 4.

Each of the connectors is recessed in its bore area as indicated at 14 to provide substantially annular contact surfaces 15 and 16 of narrow width which terminate in said bore. This insures the development of a high contact force permit of contact area between the connector clamp and the conductor to which it is attached. When the screws 10 and 11 are drawn down, the clamping connector is constricted about the conductor; and since out the entire circumference of the conductor, except for the narrow space 9 as shown in Figure 2 (i.e. they substantially encircle the conductor) and since in high frequency applications the current flows in the outer skin surface, the connector will have a current-carrying capacity at least substantially equal to the current-carrying capacity of the conductor to which it is attached The shorting strap 7 preferably is made of copper or other conductive material and is disposed with its major faces 17 and 13 substantially normal, i.e. about 90, to the plan or axis of the conductors 3 and 4. By providing a strap 7 which is disposed transversely to the axis.

- of the conductors 3 and 4, high frequency current flow- .Referring to the drawing, the shorting strap 2 is shown in Figure 1 as positioned over a pair of axially parallel conductors 3 and 4 which, as mentioned previously, may be the legs of an inductor coil made of hard copper tubing. The strap 2 includes a pair of clamping connectors 5 and 6 and a strap 7 which is joined to the connectors.

Each of the clamping connectors has a body which 'is of generally circular configuration, as shown in Figure 2. Each body is provided with a bore 8 which is eccentric with respect to the axis of the body. The connector is split along its length, as indicated at 9 in Figure 2, to provide the desired clamping action when theconing from one of the conductors to the other through the shorting strap will tend to flow over the whole width "of the strap, i..e. the surfaces 17 and 18, rather than along the narrow edges of the strap. This insures maximum uniformity of current distribution in the shorting strap. The width of the strap 7 is preferably about equal to or greater than the circumference-of the conductors 3 The strap 7 is preferably offset from its normal plane,

as indicated at 21, to provide limited flexibility in the unit to accommodate any outer parallelism which may exist in conductors 3 and 4.

By providing the fastenings 10 and 11 in the portions of the clamping connector remote from the shorting strap 7 and outwardly of the annular clamping surfaces 15 and 16, there will be little flow of high frequency current through the fastenings 10 and 11, and they may be formed of steel and may be drawn up with considerable torque to insure a tight connection between the clamping connectors and the conductors. A spreading screw 22, as shown in Figures 1 and 4, may be provided in each of the clamping connectors. The screw is threaded into the arm 12 of the connector and is disposed to engage the flat surface '23 of the opposite arm 13, as shown in Figure 4. When the shorting strap is to be adjusted, the screws 10 and 11 are loosened in Patented Apr. 26, 196 0 7 both clamping connectors, and the spreader screws 22 are drawn down. This tends to spread the arms 12 and 13 of the clamping connectors, loosening their grip on the conductors 3 and 4. The strap may then be moved along the conductors 3 and, 4v to the desired location. The spreading screws 22 then will be backed-off, and the clamping screws 19 and 11 will be drawn down to again constrict the connectors and make the desired low-resistance connection between the shorting strap and the conductors.

In a typical shorting strap for use on 1 /2" diameterconductors, the connectors may have an outer diameter of about 2 /2 and may be about 2" long. The narrow contact surfaces may be about wide. The strap may be about 2%" wide and A thick. The connector maybe formed of brass, the connecting screws ofstecl; and the strap of cold rolled electrolytic copper sheet.

I claim:

1. A connector for high-frequency electrical services comprising a slitted, single-piece clamping connector body havinga bore therein to receive a conductor, said slit in said body extending from said bore to the outer surface of said body and being directed generally parallel to the axis of said bore, narrow substantially annular contact surfaces forming part of said body at the upper and lower extremities of said bore for engagement with said conductor throughout substantially the entire circumference of the conductor, a substantially flat strap electrically joined to said body at a location substantially opposite to said slit and extending with its major faces disposed at an angle of substantially 90 with respect to the axis of said bore, andclamping means passing through said slit and received in said body remote from said annular contact surfaces for constricting said bore to bring said contact surfaces into close engagement with said conductor along surfaces substantially completely encircling said conductor and remote from said clamping means.

2. A shorting strap for high frequency electrical services comprisinga pair of split clamping connectors each including a substantially cylindrical body portion having a substantially cylindrical bore therein eccentric with respect to the axis of said body portion to receive-a conductor, said bore being undercut to provide a pair of narrow substantially annular contact surfaces forming part of said body at the upper and lower extremities of said bore for engagement with said conductor throughout substantially the entire circumference of the conductor, saidbody being provided with a slitted opening extending from said bore to the outer periphery of said body and dividing the body into two opposing arm-portions', a clamping screw passing through one of said arms and being received within a threaded opening in the other of said arms for constricting said bore to bring said contact surfaces into close engagement with said conductor along surfaces substantially completely encircling said conductor, and a substantially flat shorting strap electrically joined to each of said connector bodies with- 1 in a recess provided in the periphery thereo'fsubstantially opposite to said slitted opening therein and extending along a circumferential line substantially normal to the axis of said bore therein.

3. A shorting strap for high frequency electrical services comprising a pair of split clamping connectors each including a substantially cylindrical body portion having a substantially cylindrical bore therein to receive a conductor and having a slit in said body extending from said bore to the outer surface of said body and being directed generally parallel to the axis of said bore, a pair of narrow substantially annular contact surfaces forming part of saidbody andprojecting into said bore adjacent to the upper and lower extremities of said bore for engagement with said conductor throughout substantially the entire circumference of the conductor, means received in said body remote from said contact surfaces for constricting said bore to bring said contact surfaces intoclose engagement with said conductor along a pair of substantially completely encircling surfaces on said conductor, and a substantially flat shorting strap electrically connected to each of said clamping connector bodies at the periphery thereof substantially opposite to said slitted opening therein and extending along a circumferential line substantially normal to the axis of the bore therein, said strap having a portion offset from the general plane of said strap to provide limited flexibility in said strap between said connectors.

4. A shorting strap for high frequency electrical services comprising a pair of clamping connectors each including a body portion having a bore therein to receive one of a pair of conductors, two spaced opposing arm portions-projecting from the body portion and defining a slitted opening therebetween which extends from said her to the outer periphery of said connector, at least one narrow substantially annular contact surface forming part of said body at one of the extremities of the body for engagement with said conductor throughout substantially the entire circumference of the conductor, clamping means disposed at said arm portions and remote from said annular contact surface for constricting said bore by closing said slitted opening to bring said contact sur face into close engagement with said conductor along a surface substantially completely encircling said conductor and remote from said clamping means, and a substantially flat shorting strap electrically connected to each of said connector bodies throughout a substantial portion of the periphery thereof at a location substantially opposite. to said slit and extending along a line directed generally normal to the axis of the bore in the body.

References Cited in the file of this patent UNITED-STATES PATENTS 1,073,670 Ford Sept. 23, 1913 2,651,767 Bergan Sept. 8, 1953 FOREIGN PATENTS 532,344 Great Britain Ian. 22, 1941 

